Many local networks use Dynamic Host Configuration Protocol (DHCP) to configure devices that join a network. When a device joins the network, the device may perform a query to locate a DHCP server and may download certain parameters that are used by the device to configure a network connection. Typically, these parameters include a network address for the device and a Dynamic Name System (DNS) server that may resolve friendly names into Internet Protocol (IP) addresses.
In a typical home or small business environment, a device such as a cable modem or Digital Subscriber Line (DSL) modem may serve as a gateway to the Internet, and may also provide DHCP and other services to devices within a local area network. Such devices are often pre-configured by a network provider with default DHCP settings that allow a user to connect to the Internet. Such default DHCP settings may include a reference to a DNS server that may be managed by the network provider and may provide DNS name resolution for any device connected to the Internet.
In some local area networks, a second DNS server may be used to provide DNS services within the local area network. The local DNS service may allow devices within the local area network to communicate with each other to share files and services within the local area network. Typically, these local connections are within the bounds of the local area network and are not accessible from the Internet.